Method of uniting and molding composite layers.



UNITED 'sr-Arrns PATENT orrion.

ANDREW THOMA, CAMBRIDGE, MASSACHUSETTS, ASSIGNOR TO THOMA CORPORATION, OF PORTLAND, MAINE, A CORPORATION OF MAINEQ;

7 METHOD OF UNITING AND MOLDING COMPOSITE LAYERS.

Specification of Letters Patent.

Patented Aug. 20, 1907.

Application filed December 31, 1966. Serial No. 350,276.

To all whom it may concern:

Be it known that 1, ANDREW THOMA, a citizen of the United States, and a resident of Cambridge, in the countyof Middlesex and State of Massachusetts, have invented an Improvement in Methods of Uniting and Molding Composite Layers, of which the following is a specification.

In the different manufactures where it is required to unite several thicknesses of stiff leather or the like to form a heavy thick unyielding piece, the common practice is to apply a cheap paste or gummy solution in copious amount to the respective leather pieces, and

' then, having immediately assembled the pieces while still wet with the copious applications of paste, the piled up pieces are placed under pressure and held tightly together until the paste has stuck them together, when they are dried and then finally again pressed to their ultimate shape. This process is inexpensive in materials, but very expensive in labor and time, as well as requiringcare and skill to prevent the leather pieces from cracking or checking and gapping between layers,

' due to their shrinkage after the undue wetting and soaking with the paste.

"My invention aims to do away with the long delay above required and besides, to produce a superior article.

- By my method I entirely eliminate the soaking with paste, the preliminary compression and the drying,

my method also permitting the final molding or compression of the composite leather article to take place at any desired length of time after the original cementing, so that thereby a large number are permitted to accumulate during the cementing process to be molded "duly hard or horny, as is sometimes the case with sole leather, for instance, or such as is used for making heels, I first temper it by dipping it in water or otherwise rendering it properly limbcr and moldable. Then I apply to one side of the leather an exceedingly thin film or coating of cement capable of liquefying under heat and of becoming soft under great pressure. A second piece of leather is then applied directly to the first, the cementholding it sufficiently to maintain its proper position. The top side of the second piece is similarly coated with. a-thin film of the same strongly adhesive cement liqucfying under heat. A third piece of leather is placed thereon and in turn is cemented-and so on with as many layers as required for the article which is to be formed. No nailing is necessary to hold the pieces securely in place, although if desired a single nail may now be inserted, depending to some extent upon the form and kind of mold or press to which the stacked pieces of leather are to be'subjected.

Having thus quickly and to some extent imperfectly put together the required thicknesses of superposed pieces of leather, they may be left indefinitcly'while the workman repeats the process with other pieces,

thereby accumulating a large number of the cemented products. When a sufiiciently large number have accumulated and a convenient time arrives for subjecting them to the molding process, the individual pieces are placed rapidly in the press and quickly and powerfully compressed, the result being that the sudden and enormous pressure exerted upon the leather pieces causes the thin film of cement to flow and spread and stick with perfect uniformity and adhesion at every point throughout the entire contacting surfaces. The original cementing of the pieces may have been more or less imperfect and they may not have been pressed together sufficiently to cause them to. unite excepting just sufficiently to hold them in proper relative position, andv the cement may to all external appearance have become practically dry or invisible, showing little signs of stickiness, yet under the pressure it becomes active as if freshly applied and produces a strong union. As this union takes place not under any preliminary flat pressing such as has heretofore been required for permitting the previously used paste to dry out to some extent, but under the enormous molding pressure referred to, and as the leather is in the proper condition for molding, the result is that there are no gaps or ch ccks and the union is practically perfect throughout the entire areas of the joined surfaces.

My invention will be perhaps better understood by referring to the manufacture of heels by way of illustration. As at present made the lifts are coated 0r flooded copiously with paste or gummy solutions such as dextrin, thereby soaking and softening the leather. The adhesion of the paste is slow-acting and takes place only after the drying out of the water has been accomplished, so that it is necessary to keep the heels under pressure during the long time required for drying out the paste while the gummy matter is still wet and soft. Also, as the tendency of the leather to separate is very strong, it is found necessary to nail the lifts together as the heel is built up in order to maintain the proper position of the lifts during the pressing and drying period. This pressing of the heel at this wet stage of its manufacture is merely a flattening or holding down of the lifts uponone another. Notwithstanding this preliminary pressing, it is not sufficient to prevent the placed in the molding press which, although sufficiently powerful to press the pieces into a shaped heel, cannot close a gap or check between the layers due to the defective union above mentioned, for the reason that when the dextrin or the like has become dry, it is no longer sticky. Hence considerable skill is required in subjecting the layers and heel to the various treatments for the right length of time, and in the right manner for securing proper results. By my method all this care and delay are entirely eliminated. The operator simply places on the bench a lift or layer of heel stock (my invention not being restricted to leather, but including usual substitutes and other flat layer-like pieces commonly assembled as stated), and coats it by one blow of a cement pad, (the lift being engaged by a cleat or suitable jaws or any means for preventing its being lifted by engagement with the cement pad), and'then lays upon this cemented lower lift or layer another layer which is instantly cemented in a similar manner, and thena third layer placed thereon, which is in turn cemented and so on until the whole is built up to the right height. The rand is then put in place in the usual manner, and if desired a nail is .driven through the entire heel. The, next heel is built up, quickly in the same manner, the successive heels as finished beingaccumulated; and finally the entire accumulation is passed one by one quickly through the molding press as already explained. The cement used sets and adheres instantly without softening or influencing the leather, so that the heel, once cemented,

may be nailed, randed and pressed to a finished article at once as a continuous process and quickly. It simply requires the short amount of time for performing in the quickest manner possible the different steps mentioned, no delay for drying or preliminary pressing of nailing and the like being required. An exceedingly small amount of cement is used, the best results being secured with the thinest and lghtest coating. The leather is tempered before the heel is assembled instead of being tempered by drying out the surplus moisture after the heel has been assembled. Therefore when the heel has been assembled it is ready to be compressed instantlyl On the other hand, it need not be compressed at once, but even greater expedition can be secured by Waiting until the molding press can be run for a large quantity of heels as explained.

Another distinct advantage is that my invention enables the manufacturer to reduce simultaneously a large number of heels to one and the same thickness or height. As the layers of each heel are held properly and immovably together solely by the cement without any nail, a large number can thereby be simultaneously planed or shaved off to one and the same level (not possible before because of the necessary presence of a holding nail in each heel). While various kinds of cement maybe used meeting the requirements above mentioned, I prefer to employ the cement set forth in my app ication Serial No; 340,337. v J

One of the greatest advantages, so far as my invention relates to heels is the immediate assembling of theheels without the use of moisture-adding binding agents and the immediate progress of the heel to theranding and pressing operations, so that the entire process from start to finish is a matter of only a few minutes,'whereas heretofore it has taken days to make a heel.

When my method is properly carried out to its fullest together in the presence of a cement capable of beconr ing soft and spreading underpressure forms them into a, compact mass or body, and this body is not disturbed by subsequent vertical pressure but instead is improved. Even when it is desired to nail the heels made by my method the nailing may all be done at one time when a large number of the cemented and assembled hcels have been accumulated, the same as the molding may be similarly done as already explained. In each instance this results in a material saving of time.

While my method is particularly adapted to, and intended for, heels, it is not restricted thereto. For instance it isof advantage in laying soles, and in fact wherever great pressure is feasible and it is practicable to employ a quick-setting cement capable of softeningand spreading under great pressure.

Having described my invention, wliatI claim as new and desire to secure by Letters Patent is:

1. The herein described method, consisting of interposing between adjacent layers of leather :1 thin film of strongly adhesive pcrnmnently sticky cement ,liquefying under heat, and then suddenly and momentarily applying powerful pressure to the superposed layers, and liquel'ying and spreading the cement by said sudden and severe pressure.

2. The herein described method, consisting of coating oneside of a leather piece with a thin lilm'of strongly adhesive permanently sticky cement lionefying under heat, applying thereto a. second layer of leather; similarly conting the outer surface of said second piece, applying thereto a third layer of leather. and so on, alternately applying cement and leather until the desired thickness is built up. and men liquefying and spreading,' the cement simultaneously between all of said layers by subjecting the assembled thicknesses too powerful compression.

3. The herein described method, consisting of placing a series of flat pieces on top of each other. each piece being thinly coated with strongly adhesive cement capable of liquefying under moderate heating, then driving a nail through all of said pieces and finally liquei'ying and spreading the cement simultnneously between all offthe fiat pieces by means ofrenormons pressure.

4. The herein described method, consisting of interposlng between adjacent layers of leather :1 thin layer 'of" strong. permanently adhesive cement capable of softening and spreading and becoming freshly adhesive "under great action said interposed layer of cement and thereby unite pressure. and then subjecting the superposed layers of leather to a powerful compression suflicieut to. bring into the layers of leather.

5. The herein dcsci ibed method. consisting of first loinpering the individual layers, then stacking the lnyorsonc upon the other, first havingiapplied bctwecu succc sivo layers a thin coating of quick-setting. pcrmancnlly sticky cement llquefying under pressure. 'and finally subjecting the stacked and cemented layers to heavy pressurc.

(i. The herein described method, consisting of first teln- .pering the leather layers. then applying between succcssivcv layers a thin film of strongly adhesive cement cnpnblo'ot' liquefying. under pressure. and assembling the layers one on .top of another. and then molding'the assembled cemented layers under great pressure.

i In testimony whereof. l have signed my name to this specification, in the presence of two subscribing witnesses.

ANDREW ,TIIOMA. Witnesses (lno. H. MAxtrnnL,

M. J. Smnnme. 

